1. Field of the Invention
The present invention relates to a wafer retainer and, more specifically, to such a wafer retainer to be used in a wafer carrier to retain storage wafers in position.
2. Description of Related Art
A wafer carrier is adapted to transfer wafers between a stoker and a load port, or to temporarily hold wafers in a stocker. U.S. Pat. No. 6,082,540 discloses a wafer carrier having two retainers installed in two rows of openings in the inner surface of the door panel thereof so that spring arms of the retainer hold individual wafers in position against vibration during transfer.
Because two rows of openings must be made in the inner surface of the door panel and the retainers must be provided with plug pins and O-rings for positioning in the openings, the fabrication and installation of the wafer carrier are complicated. The openings in the inner surface of the door panel may cause the air leak problem of wafer carrier and cause a barrier to the procedure of cleaning and drying the wafer carrier. Furthermore, the spring arms are unstable since there is only the plane frame base itself against the torque of the corresponding storage wafers. Because the frame base of the wafer retainer is not well supported at two corners of the inner surface, the holding down pressure from the spring arms is not evenly applied to the corresponding storage wafers. Further, because the spring arms are alternatively stopped at the storage wafers at one contact point of the left or right side, the storage wafers tend to be tilted. There is another known design, which uses two contact points to hold down each storage wafer. However, the two contact points increase the chance of friction, resulting in the formation of particles that will contaminate the storage wafers.
Therefore, it is desirable to provide a wafer retainer for wafer carrier that eliminates the aforesaid drawbacks.
The main object of the present invention is to provide a wafer retainer, which can easily be installed in the inner surface of the door panel of a wafer carrier without making openings in the inner surface of the door panel so that the wafer carrier is maintained in an airtight status when the door panel closed, and the door panel is easily cleaned and dried. It is another object of the present invention to provide a wafer retainer, which keeps the spring arms to hold the corresponding storage wafers stably in the wafer carrier so that the service life of the spring arms is greatly prolonged. It is still another object of the present invention to provide a wafer retainer, which enables the holding down pressure to be evenly distributed from the spring arms to the corresponding storage wafers, so as to minimize the formation of friction between the spring arms and the corresponding storage wafers and to prevent the generation of particles, and to save the expensive material cost of the retainer. To achieve these and other objects of the present invention and according to one aspect of the present invention, the wafer retainer is installed in the inner surface of the door panel of a wafer carrier. The door panel has a recessed area in the inner surface, one lateral sidewall at one side of the recessed area, at least one retaining portion at the lateral sidewall of the recessed area, and at least one locating element at the inner surface adjacent to the lateral sidewall of the recessed area. The wafer retainer comprises a frame bar, a plurality of spring arms respectively inwardly extended from the frame bar, the spring arms each having a top end and a bottom end, at least one retaining portion respectively extended from the frame bar and adapted to engage the at least one locating element of the inner surface of the door panel, and at least one positioning element respectively downwardly extended from the frame bar and adapted to engage the at least one retaining portion at the lateral sidewall of the recessed area of the door panel. Because the wafer retainer can be positively secured to the inner surface of the door panel without making openings in the inner surface of the door panel, the wafer carrier is maintained in an airtight status after the door panel closed, and the door panel is easily cleaned and dried. According to another aspect of the present invention, an other lateral sidewall is formed at the other side of the recessed area and at least one other locating element is provided at the inner surface of the door panel adjacent to an other lateral sidewall, and the wafer retainer has an other frame bar arranged in parallel to the frame bar, the other frame bar having a plurality of inwardly extended spring arms, the spring arms of the other frame bar each having a top end and a bottom end. The other frame bar is located on the at least one other locating element of inner surface of the door panel, and then the at least one retaining portion of the frame bar is located on the at least one locating element of the inner surface of the door panel to force the positioning element of the frame bar to be fastened to the respective retaining portion of the lateral sidewall of the recessed area. Because the spring arms are alternatively arranged at different elevations with the respective top ends aligned in a line, the size of the wafer retainer is minimized to diminish material consumption. According to still another aspect of the present invention, the spring arms each further comprise a protruded portion downwardly extended from the respective bottom end and stopped at the lateral sidewall of the recessed area of the door panel, so that the holding down pressure from each spring arm is evenly employed to the corresponding storage wafer because of a reverse torque from the protruded portion. According to still another aspect of the present invention, the top ends of the spring arms are aligned in a line corresponding to the centerline of the door panel, and respectively disposed in contact with a respective storage wafer at one contact point so as to prevent the wafer tilted and to minimize friction between the respective storage wafers and the respective spring arms.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.